The present invention relates to a novel method for the preparation of chlorosilanes from organosilanes and organopolysilanes. Further, the present invention provides a simpler route for the synthesis of useful aminosilanes.
Chlorosilanes, and particularly chlorodisilanes, provide a desirable starting material for the synthesis of aminosilanes which are used extensively as silylating reagents in thin layer resist imaging processes (TLI) used for extreme ultraviolet (EUV) lithography.
One approach to imaging a circuit pattern onto a substrate involves introducing silicon into the surface layer of a photoresist material after exposure, as described by Coopmans, et al. "DESIRE: A New Route to Submicron Optical Lithography", Solid State Technology, pp. 93-97, June 1987. In this process, a resist material that will react with silation reagents is coated onto a substrate or an intervening planarizing layer and a circuit pattern is produced on the resist material by a standard UV exposure. Various modifications to Coopmans original silylation process, as well as alternative methods of employing silicon-based chemistry in top surface imaging (TSI) processes have been disclosed. However, at some point in all the above described TSI processes the resist coated wafer is subjected to silylation, generally by an organodisilane and preferably by an aminodisilane, such as dimethylaminopentamethyldisilane (PMDS).
The aminosilanes and aminodisilanes useful for the TSI processes discussed above can be readily produced by reaction between a chlorosilane or chloropolysilane and a nitrogen containing compound such as an amine or ammonia. While there are numerous methods for preparing aminosilanes or aminopolysilanes from organohalosilanes known in the art, the preparation of organochlorosilanes starting materials from organosilanes can be difficult. Existing synthetic methods can be complicated, difficult to control, produce low yields, require complicated steps to separate byproducts, or require expensive starting materials.
Ishikawa et al. in U.S. Pat. No. 5,258,535 disclose a method for the synthesis of partially chlorinated organosilane or organopolysilanes. The method comprises the stepwise substitution of Cl for H on a Si atom by the use of CuCl.sub.2 in the presence of a CuI catalyst. While the method of Ishikawa et al. is successful in producing partially chlorinated organosilane and organopolysilane compounds, it suffers from two distinct disadvantages; HCl, produced as a reaction byproduct, can react with the chlorinated organosilane product, and another reaction byproduct CuCl can be difficult to separate from the chlorinated organosilane product. In both cases the reaction byproducts produced by the method of Ishikawa et al. can affect both the quality and quantity of the desired chlorinated organosilane reaction product. Moreover, the synthesis of Ishikawa et al. requires the use of 2 equivalents of the CuCl.sub.2 reactant for each Cl atom added to the organosilane.
What is needed is a synthetic method that offers the ability to produce partially chlorinated organosilane or organopolysilane materials and eliminates undesirable reaction byproducts which can affect either, or both, the quality and quantity